Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Thursday, September 17, 2015

Scaphonyx, Hyperodapedon minor and a site update

The final example of four-ex-saurischians is Scaphonyx fischeri. A big thanks to Mike Benton for helping me with Hyperodapedon minor. Today The Theropod Database was also updated, and the next update in October will feature all the new SVP 2015 information.

Comments- The holotype was discovered in 1902, and initially announced by Woodward in 1903 before being described and named by him in 1907. White (1906) first published the name in a note in Science, but did not provide a description or definition (ICZN Article 12.1), making the name a nomen nudum. Woodward (1907) identified Scaphonyx as a Euskelosaurus-like dinosaur based on several characters. First, the dorsal centrum lacks a parapophysis, supposedly unlike 'anomodonts' (under which he included pareiasaurs, procolophonids and therapsids), but rhynchosaurs (which Woodward classified as rhynchocephalians) possess the same state as Scaphonyx. Second, the cervical supposedly resembled Euskelosaurus, but this was based on a specimen (BMNH R2791) now referred to Erythrosuchus (as foreseen in Woodward's postscript). The large pedal ungual I with obliquely curved unguals was compared favorably to sauropods, but is also present in derived hyperodapedontines. Finally, a pedal digit with four phalanges was considered similar to dinosaurs and unlike 'anomodonts', but rhynchosaurs have three pedal digits with this many phalanges as well, and the digit closely matches manual digit III of Alemoa Hyperodapedon. Woodward's 1907 paper was actually written in 1904, and when reprinted in 1908 he included a postscript which recognized BMNH R2791 as non-dinosaurian. As he compared it favorably to Erythrosuchus (considered by Woodward to resemble both 'anomodonts' and 'belodonts'- the latter containing parasuchians and aetosaurs), Woodward now considered Scaphonyx an 'anomodont'.
Huene (1908) noted Scaphonyx was unlike dinosaurs in the presence of postaxial intercentra, cervical diapophyses and parapophyses which are placed high on the vertebra, and dissimilar unguals. He suggested it might be a therapsid or parasuchian. In 1911, Huene proposed Scaphonyx and Erythrosuchus were members of his new 'thecodont' group Pelycosimia, which continued through 1926 when he gave Scaphonyx its own family. In 1929, Huene finally recognized the similarity between Scaphonyx and rhynchosaurs, assigning the genus to the group.

While long considered a valid genus of rhynchosaur, Langer (1996; published in Langer and Schultz, 2000a) proposed Scaphonyx fischeri's holotype is indeterminate, as multiple species are known from the Alemoa member (mariensis, sanjuanensis, and what would be named huenei) which have only been distinguished using cranial characters. Although huenei is not known from postcrania (so can't be compared to fischeri), mariensis and sanjuanensis have not had their vertebral or pedal anatomy compared in detail in the published literature. Indeed, Alemoa rhynchosaurs have not had their postcrania well described in over seventy years. Given these facts and that I lack access to both Langer's thesis and mariensis' original and only published description, I only consider it provisionally indeterminate here. Additional specimens assigned to S. fischeri by Huene (1926, 1942) have been considered indeterminate or referrable to S. sanjuanensis (Langer and Schultz, 2000b; Montefeltro, 2008; Langer, pers. comm. 2015).

As a bonus, since I make a short entry for every species of a genus that I use on The Theropod Database, I came across Hyperodapedon minor. Barely any info was present online, or in the literature.

H. gordoni Huxley vide Murchison, 1858
?= Hyperodapedon minor Burckhardt, 1900b
= Stenometopon taylori Boulenger, 1904Early Norian, Late TriassicLossiemouth Sandstone Formation, ScotlandComments- The citation for Murchison (1858) is often listed incorrectly, misspelled 'Murchinson', cited as 1859, with an erroneous title, and pagination from Huxley's 1869 paper.Hyperodapedon minor- This species was established by Burckhardt (1900b; page 492) for two small maxillae and a mandible from Warwickshire which were mentioned in a footnote by Huxley (1869) as H. gordoni. Only a few statements were made about H. minor in Burckhardt's work, with the only proposed distinguishing character being a more posteriorly extensive dentary tooth row than H. gordoni. The taxon has been virtually ignored in the literature since, though Huene (1942) did say its distinctiveness from H. gordoni is unfounded and that it should probably be rejected. Discussion with Benton (pers. comm 2015) indicates Burckhardt only visited the BMNH, though no specimens there were indicated as belonging to this species. Based on Benton's unpublished thesis notes, I believe BMNH R3150 (listed as "Partial skull 18 pieces, some fitting: palate views of mx, pal etc - small animal") is the best possibility for being H. minor's holotype, though it's possible the holotype has remained unnoticed or become lost. Regardless, the fact all diagnostic Lossiemouth Sandstone rhynchosaurs have been referred to H. gordoni suggests H. minor is similarly referrable.References- Murchison, 1858. On the sandstones of Morayshire (Elgin, &c.) containing reptilian remains; and on their relations to the Old Red Sandstone of that country. Quarterly Journal of the Geological Society of London. 15, 419-439.
Huxley, 1869. On Hyperodapedon. Quarterly Journal of the Geological Society of London. 25, 138-152.
Burckhardt, 1900a. On Hyperodapedon gordoni. Geological Magazine. 7(12), 529-535.
Burckhardt, 1900b. On Hyperodapedon gordoni. Geological Magazine. 7(37), 486-492.
Boulenger, 1904. On reptilian remains from the Triass of Elgin. Philosophical Transactions of the Royal Society of London B. 196, 175-189.
Huene, 1942. Die fossilen Reptilien des sudamerikanischen Gondwanalandes. C. H. Beck, Munich. 342 pp.
Benton, 1981. The Triassic reptile Hyperodapedon from Elgin, functional morphology and relationships. PhD thesis, University of Newcastle upon Tyne. [? pp].